God wants our conscience to be certain and sure that it is pleasing to Him. This cannot be done if the conscience is led by its own feelings, but only if it relies on the Word of God.
Martin LutherAll these things He must be in me, abiding, living, speaking in me; that I may be the righteousness of God in Him (2 Cor. v. 21); not in love, nor in gifts and graces which follow; but in Him.
Martin LutherWhen God works in us, the will, being changed and sweetly breathed upon by the Spirit of God, desires and acts, not from compulsion, but responsively.
Martin Luther